1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to transmission of rights object information, and more particularly, to transmitting rights object information between a device and a portable storage using a current permission status format (CPSF) that includes permission information of a rights object so that overhead is reduced during transmission of rights object information.
2. Description of the Related Art
Recently, digital rights management (DRM) has been actively researched and developed. Some commercial services have already implemented DRM and others plan to. DRM is needed because of the following characteristics of digital content. Unlike analog data, digital content can be copied without loss and can be easily reused, processed, and distributed. However, a large amount of cost, labor, and time are needed to produce digital content. When digital content is copied and distributed without permission, producers lose profits, and motivation to produce is discouraged. As a result, the development of digital content businesses is hampered.
There have been several efforts to protect digital content. Conventionally, digital content protection has concentrated on preventing non-permitted access to digital content, that is, permitting only people who have paid charges to access the digital content. However, when a person who has paid charges intentionally distributes the digital content to other people, they can use the digital content without paying charges. To solve this program, DRM was introduced. In DRM, anyone is allowed to freely access encoded digital content, but a license referred to as a rights object is needed to decode and execute the digital content. Accordingly, the digital content can be more effectively protected by DRM.
The concept of DRM using conventional technology will be described with reference to FIG. 1. DRM relates to management of content (hereafter, referred to as encrypted content) protected using a method such as encryption or scrambling and rights objects allowing use of the encrypted content.
Referring to FIG. 1, a DRM system includes devices 110 and 150, e.g., mobile terminals, wanting to access content protected by DRM, a contents issuer 120 issuing content, a rights issuer 130 issuing a rights object containing a right to access the content, and a certification authority 140 issuing a certificate.
In a DRM system, the device 110 can obtain desired content encrypted from the contents issuer 120. The device 110 can obtain a license to playback the encrypted content from a rights object received from the rights issuer 130. Then, the device 110 can playback the encrypted content. Since encrypted content can be circulated or distributed freely, the device 110 can freely transmit the encrypted content to another device 150.
The device 150 needs the rights object to playback the encrypted content, which can be obtained from the rights issuer 130.
Meanwhile, the certification authority 140 issues a certificate indicating that the contents issuer 120 is authentic and the devices 110 and 150 are proper devices. The certificate may be embedded into devices 110 and 150 when the devices 110 and 150 are manufactured, and it may be reissued by the certification authority 140 after a predetermined period has expired.
In addition to a technique of directly transmitting a rights object or encrypted content between the devices 110 and 150 as shown in FIG. 1, a technique of transmitting a rights object and encrypted content through a portable storage from one device to another device has been suggested recently.
Generally, a portable storage has a lower data storage capacity or data processing speed than a device such a mobile terminal. Therefore, efficient management of data transmission between the device and the portable storage is needed.